The invention relates to an absorbent article for application to human or animal skin surfaces in the region of wounds, consisting of an outer covering which is permeable for liquid substances, and of an inner layer which is surrounded by the covering and which consists essentially of a mixture of an amount of strongly osmotically active substances with an amount of osmotically comparatively weak or osmotically inactive substances, such as cellulose.
An absorbent article of the type mentioned at the outset is revealed in the applicant's DE 100 59 439. The known absorbent article has proved very useful in practice, but there is a need to strengthen the absorption efficiency, especially for moderately to heavily discharging, infected wounds from which the wound exudate can be absorbed more efficiently from the depth of the wound floor.
This object is achieved by an absorbent article of the type in question in which the inner layer is filled with osmotically active substances in such a way that it is possible to exert on a wound, with the wound fluids contained therein, an osmotic pressure via which the wound fluid can be removed from the organism to be treated, and thus it is possible to assist both in the surfaced wound region and in the depth of the tissue a normal interstitial hydration of tissue by directing endogenous fluids in their direction of flow to the patient's skin surface into the absorbent article, and keeping them there.
The inner layer is designed in such a way that the mass per unit area is at least 420 g/m2, with the mass per unit area of the proportion of osmotically active substances which is uniformly distributed therein being at least 200 g/m2.
The concepts of treating chronic wounds and oedema therapy often cannot be separated, because inflammatory processes, infectious events and leaks from vessels occur with one type as well as the other.
If oedematous fluid resulting from pathological processes enters the cells of a tissue, these cells are compressed. Their distance from vessels which provide nourishment or transport away grows, diffusion processes become more difficult, metabolic products accumulate and oxygen becomes rare. An additional factor is that metabolic products escape from dying cells, so that sugar catabolites such as lactic acid (lactate from glycolysis) or else citric acid accumulate and bring about active breakdown of collagen and destroy tissues.
Theoretically, this breakdown of tissue, which is equivalent to the production of a wound, underlies a large number of further processes. Activated leucocytes, growth factors adhering to fibrin (growth factor trap hypothesis) and hypoxic areas assist the tissue breakdown.
The causes of the perturbing potency lie in the presence of hyperhydration and long residence times of water in tissue. A therapeutic approach taking account of this realization is vacuum therapy, in which the wound region is exposed to specific subatmospheric pressures by means of closed systems. The healing results are impressive.
The disadvantages are that this therapeutic approach is a very costly and elaborate procedure requiring apparatuses. It is therefore advantageous to apply analogous mechanisms following different physical laws to the wound region, for example by a dressing according to the invention with high osmotic subatmospheric pressure. Oversized amounts of water-storing polymers, e.g. 200 g/m2, fulfil this task and are useful in that water molecules abandon contact with other water molecules only on application of a high separation force. The circumstance that a molecule as small as water must be heated up to 100° C. in order to achieve this separation proves this.
Accordingly, water molecules in deep layers of tissue are also reached, and the excess aqueous exudates there are sucked out, via the suction on water molecules located on the surface. Cohesive forces of the water permit chain-like removal of water molecules as far as the site of development of the oedemas.
This suction achieves a large number of advantages. Collagen-degrading substances such as citric acid or lactic acid which are present in the oedema and there actively maintain the wound are removed. Diffusion processes become easier again, the cells receive oxygen, building substances and mediators such as growth factors. Collagen synthesis can start.
By utilizing the unwanted exudate as carrier substance and as rinsing agent for the wound region, substances present in the exudate are rinsed through a plurality of tissue layers and cleanse the layers of the wound.
Known wound-contact materials with superabsorbent substances have the property of binding escaping water in order to avoid noticeable escape thereof. Although a “depth effect” is mentioned, it is not defined. By contrast, the present absorbent article achieves, for example with leg ulcer (VLE), a depth effect as far as the insufficient vein and thus as far as the perivenous tissue and its oedema. A swelling process in the absorbent article achieves adaptation to the wound floor in the sense of wound morphology adaptation because of the displaceability of the saturated superabsorbent granules.
The absorbent article may be present in a dressing as combination product. Additional pockets or coverings with perforated films in the sense of wound-distance lattices can be inserted into the absorbent article. It can also be used here adjacent to other dressing materials such as foam dressings, alginates, hydrophilic fibres, polyhexanides and carriers, CMC (carboxymethylcellulose), hydrophilic fibres, hydrocolloids, lipocolloids, honey, activated carbon, silver, cellulose, drugs, hydrogels, detergents such as surfactants and poloxamers and carriers thereof, other superabsorbent-containing articles or mixtures of such devices. Depending on the mode of use, the product can be placed with one side towards the wound, in which case the absorbent article has indirect contact with the wound; it can also be directed with the other type of dressing material towards the wound, in which case the type of dressing material forms a flow-through element through which the absorbent article draws the exudates and thus increases its absorption capacity and prolongs the time it is left on the wound.
The covering may consist of more than one film or cover, for example in such a way that a nonwoven is present on one side and a water-resistant or water vapour-permeable backsheet is present on the other side. Another possibility is to use a three-dimensionally shaped wound-distance lattice on one side and a cover with special functions such as the carrying of activated carbon or antiinfective agents on the other side. Two homogeneous covers or mixing of different covers are possible.
The covering consisting of one or more cut sections should preferably be bonded, ultrasonically welded, thermally generated or mechanically accomplished. The seam preferably does not form the outer edge of the product, but leaves an unsewn material portion which has uni- or multilamellarly flexible and soft product edges. This covering may be partly or entirely closed in the periphery, remain open on at least one length or have duplicatures.
Besides a spatial proximity of products next to the absorbent article within a covering, it is possible for the substances mentioned, such as foam dressings, alginates, hydrophilic fibres, polyhexanides and carriers, CMC, hydrocolloids, lipocolloids, honey, activated carbon, silver, cellulose, drugs, hydrogels, detergents such as surfactants and poloxamers and their carriers, other superabsorbent-containing articles or mixtures of such materials themselves to be present in the absorbent article, for example in such a way that the superabsorbent granules are incorporated into materials of this type, also in addition to other layers which comprise the superabsorbent particles or other osmotically active substances.
One embodiment would be incorporation of superabsorbent substances into hydrophilic fibres which are present as carrier substance therefor. It is possible for additional cover layers of other materials such as cellulose to be present within a covering of the inner layer, this product of superabsorbent substances, hydrophilic fibres, cellulose cover layer or cover layer made of hydrophilic fibres and covering is present in a second covering which additionally comprises at least one of the materials mentioned. This may also be present in this covering alone or adjacent to further materials in an additional covering, so that an interior and two or more coverings are present in the overall product. Intermediate layers may be disposed between these and may have a waterproof, water vapour-impermeable, air-permeable, semipermeable or other type of configuration.
One possibility for ensuring the dimensional stability is firm pressing of the aforementioned substances of the absorbent article, with adhesives not necessarily being required.
The result is a product which includes materials such as CMC, hydrophilic fibres, alginates or other substances of those mentioned in covered form, with the purpose of redrying other materials of the dressing by the osmotically more active materials such as granular superabsorbent substances, and therefore extending the useful life of these materials and their functioning and therefore saving costs, material and care time. In parallel, phases without disturbance of the wound are prolonged, stable temperature conditions in the wound, which is important for repair processes, are achieved, and there is a bilateral interaction of the flat sides of the materials. This is because, on the one hand, these materials act in known form beneficially in the direction of the wound on the wound region, whereas they experience redrying on their reverse side facing away from the wound due to other portions of the dressing material. The materials applied closer to the wound thus display their effect, and the opposite ones can bring about a flow-through rinsing through themselves into the other portions of the dressing material.
The superabsorbent substances, chiefly granules, can be pressed into or introduced into fibre mats, but can also be bonded in, welded or fixed in other ways. Two cover layers are able here to cover a mix of cellulose and superabsorbent substances which are produced for example as airlaid mat. The superabsorbent substances can, however, also be incorporated into all other known materials, especially into hydrocolloid fibres, alginates or a blend of different substances of the type mentioned or with third materials.
Two layers of cellulose with intermediate superabsorbing substances (without cellulose) as sandwich arrangement are likewise conceivable.
Since a change of dressing is associated with a reduction in the temperature of the wound region, it is conceivable to supply the absorbent article with reagents which keep the wound temperature stable in the sense of a controlled, biocompatible, exothermic reaction. Chemical reactions such as processes based on pepper can be taken into account, especially because these will also set up an additional osmotic suction.
The product can be used as part of a compression therapy, dressing as part of a therapy for compartmental syndrome or in vacuum therapy by means of subatmospheric pressure. In the latter case, the two types of pressure, subatmospheric and osmotic, are added together so that a very sufficient oedema therapy results.
Known dressings with superabsorbent particles do not reach the necessary potency for several reasons. The known dressings' contents of superabsorbent substances are too low, and the potency of the latter is also artificially diminished because they are at a great distance from the wound region behind polyurethane foams or cellulose layers. In other products, the osmotic effect is weakened by solutions. Overall, the superabsorbent particles applied in this way have only very low osmotic potency, and their potential is exhausted within the dressing.